Horizontal boring machines are used to install utility services or other products underground. Horizontal directional drilling eliminates surface disruption along the length of the project, except at the entry and exit points, and reduces the likelihood of damaging previously buried products.
The boring operation is a process of using a boring machine to advance a drill string through the earth along a desired path. The boring machine generally comprises a frame, a drive system mounted on the frame and connected to one end of the drill string, and a boring tool connected to the other end of the drill string. The drive system provides thrust and rotation needed to advance the drill string and the boring tool through the earth. The drill string is generally comprised of a plurality of drill pipe sections joined together at threaded connections. As the pilot bore operation proceeds, the drill string is lengthened by repeatedly adding pipe sections to the drill string.
When the pilot bore operation is completed, the drill string is pulled back through the borehole during a backreaming operation, generally with the utility line or product to be installed underground connected to the end of the drill string. During this backreaming operation, pipe sections are removed from the drill string as the drill string gets shorter. Each time a pipe section is taken from the drill string. As is the case with the addition of pipe sections to the drill string, the process is repetitive.
A “driver”, or “saver sub”, is used as a connection to transmit the torque and thrust/pullback forces generated by the rotational drive of an HDD machine to a drill string. The connection comes in contact with every pipe involved with a boring operation during both boring and pull-back and thus encounters high rates of wear on the connection surfaces of the component. As such, it is beneficial to make the part easily replaceable. Further, it is beneficial to limit the wear points of the saver sub such that it is easy to replace, without requiring excessive labor to rebuild the saver sub.